Category: amino-acid
Aliases: L-Citrulline, Cit
Non-proteinogenic AA — urea-cycle intermediate generated from ornithine + carbamoyl phosphate (OTC). Found free in watermelon (Citrullus). Clinically superior to oral arginine for raising sustained plasma arginine because citrulline is not a substrate for intestinal/hepatic arginase — it bypasses first-pass metabolism and is recycled to arginine in kidney via argininosuccinate synthase (ASS) and argininosuccinate lyase (ASL). The resulting arginine supports endothelial NOS → NO (see nitric oxide synthesis) → vasodilation. Also used diagnostically (citrulline generation test) as an enterocyte-mass biomarker.
PO: 1h